Immigration to the U.S. has tripled over the last few decades. What is the impact of this flow of immigrants on the health of the larger U.S. population? Immigrants may impact the health care system by increasing demand for services or changing the specific type of services offered in areas of high immigrant concentration. Furthermore, immigrants contribute to the socioeconomic and racial/ethnic diversity of the U.S., which has implications for optimal access to and delivery of medical care and health services across various population subgroups. Understanding the characteristics and health outcomes of immigrants is prerequisite to addressing the issue of immigrants' potential impact on the U.S. population. We are interested in answering the following questions. How does the health of immigrants differ from that of natives, and along which dimensions of health? How does the health of immigrants change over time as they adapt to U.S. society? How does the immigrant-native gap in health change over time and across health outcome? Many previous studies have been plagued by limited sample size or have not used nationally representative data. Furthermore, there is no clear consensus in the literature on whether adaptation has positive or negative consequences for immigrants' health. This is partly due to the fact that many studies compare immigrants in the cross-section by years since arrival in the U.S. and infer positive or negative acculturation if groups vary significantly by duration. However, regressions done in the cross-section may lead to incorrect conclusions about assimilation if immigrant cohorts differ significantly in health or socioeconomic characteristics; in other words duration and cohort effects are confounded (Borjas, 1985). We address these shortcomings by using multiple waves of the nationally representative HRS/AHEAD data to explore the health of immigrants over time across a wide range of health outcomes. We will use logistic regression to examine immigrant-native differences in reported general health and prevalence of chronic health conditions and disability at baseline. We will then use a hazard modeling approach to 1) explore immigrant-native differences in the onset of chronic disease conditions and disability among respondents who did not have those health conditions at baseline and 2) determine whether the health of immigrants improves or worsens with time in the U.S.